@Diver, I guess the answer is, "It all depends." I mentioned the XLR out on the AOU because it's a way to get the cabinet simulation on that device to the PA if it's an integral part of your sound. As you say, many sound guys want a clean signal for purposes you cite. They use that signal for sound reinforcement in addition to your stage amp; they can process it (EQ, compression, etc.) in whatever way gives them the best overall mix. In small-medium venues where the audience is also going hear your amp directly, this would be fine. In larger (or outdoor) venue, or in situations where you amp is not part of the total mix (like zero stage volume setups using IEMs) you'd definitely want to use the DI on the Rumble 800. Also, if you use a lot of modulation and/or time-based effects, you'd want the total signal path going to the PA. If you got the spare channels on the mixer, how about sending the AOU XLR out and the R800 DI for pure sonic bliss!